1. Field of the Invention
The present invention relates generally to an efuse device and more particularly, to an efuse device which includes a graphene layer.
2. Description of the Related Art
In integrated circuits (e.g., complementary metal oxide semiconductor (CMOS) integrated circuits), it is often desirable to be able to permanently store information, or to form permanent connections of the integrated circuit after the circuit is manufactured. Fuses or devices forming fusible links are frequently used for this purpose.
Fuses can also be used to program redundant elements to replace identical defective elements (e.g., allowing for dynamic real-time reprogramming of a computer chip after the chip is fabricated). Further, fuses can be used to store die identification or other such information, or to adjust the speed of a circuit by adjusting the resistance of the current path.
An electrically programmable fuse (eFuse) device is a common fuse used in conventional integrated circuits. The eFuse device typically includes a silicide layer which is formed by silicidation of silicon. By flowing high current through the silicide layer, a large amount of heat is generated and causes a reflow of metal (such as nickel or cobalt), resulting in discontinuity of the silicide layer. That is, the silicide layer of the eFuse device is “blown”.
A conventional eFuse may include a silicide layer on a silicon or polysilicon layer, which serves as a resistor (see, for example, Bohr et al. (U.S. Pat. No. 5,708,291) and Ito et al. (U.S. Pat. No. 6,580,156). In the initial state, the eFuse silicide is highly conductive, exhibiting low electrical resistance (the “unblown” state of the efuse). When a sufficiently large current is passed through the eFuse silicide, electro-migration starts to occur. This forms a gap in the silicide layer and greatly increases its electrical resistance. When the current source is removed, the silicide remains permanently in the diffused state, the “blown” state of the eFuse.